Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.42	11.757%	$69.7587	$69.76	$69.75	$69.80
Purchase #2	$28.32	3.852%	$29.4109	$29.41	$29.40	$29.40
Purchase #3	$98.72	6.434%	$105.0716	$105.07	$105.05	$105.10
Purchase #4	$103.47	7.517%	$111.2478	$111.25	$111.25	$111.20
Purchase #5	$194.79	10.822%	$215.8702	$215.87	$215.85	$215.90
Purchase #6	$69.92	4.161%	$72.8294	$72.83	$72.85	$72.80
Purchase #7	$195.99	3.848%	$203.5317	$203.53	$203.55	$203.50
7 purchase totals =	$753.63		$807.7203	$807.72	$807.70	$807.70